The invention relates to a conveying device for the transport of workpiece carriers in accordance with the description herein.
As a rule, workpiece carriers are conveyed in a conveying device from and to one or more machining stations. Such conveying devices comprise a stationary conveyor track having at least one guide rail for the workpiece carriers and typically also comprise a corresponding drive for moving the workpiece carriers onward. Instead of such a drive, however, an incline can also be provided so that the workpiece carriers are moved onward due to gravity. To be able to stop corresponding workpiece carriers, stopping devices are provided in the conveyor track. On a corresponding stopping of the workpiece carriers, the workpieces arranged thereon can be removed and supplied to the machining station, that is, for example, to a processing machine.
Such conveying devices are already known. So-called stopping fingers that are extendably supported in the guide rail are known as the stopping device there. A corresponding stopping finger is in the respect to be provided for stopping a workpiece carrier.
A plurality of workpiece carriers having workpieces to be correspondingly machined are, however, supplied in front of machining stations so that a row of workpiece carriers accumulates before a machining station. This can be seen as a kind of buffer that is caused by the fact that the machining stations have different clock times. As soon as a workpiece carrier is to be stopped directly in front of the machining station, the stop function is subjected to the demand to stop an individual workpiece carrier.
If, however, workpiece carriers from the accumulated row of workpiece carriers should be detected in a targeted manner and should then be supplied to the working station, for example, a singularization must be carried out. Such apparatus for singularizing workpiece carriers are also already known. Two stopping fingers have to be provided here, with the workpiece carriers being able to be stopped and/or backed up by an intervention of the respective stopping finger.
The known stopping fingers are typically designed such that they engage into the guide rail on a corresponding extension movement and stop the workpiece carriers transported there as an abutment. In this respect, the stopping fingers have to cover comparatively long extension distances. For safety reasons, they have to be completely extended out of the guide rail on returning into the starting position to achieve a sufficient spacing from the workpiece carrier. The stopping fingers can typically be lowered in the base of the guide rail. Due to the long travel paths, a comparatively slow response time can be realized to stop the workpiece carrier.